After 43838a23a05f ("random: fix crng_ready() test") early boot calls
to get_random_bytes() will warn on each cpu on x86 because the crng
is not initialized. For example,
random: get_random_bytes called from start_kernel+0x8e/0x587 with crng_init=0
x86 only uses get_random_bytes() for better randomization of the stack
canary value so the warning is of no consequence.
Export crng_ready() for x86 and test if the crng is initialized before
calling get_random_bytes().
Signed-off-by: Prarit Bhargava <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: "Theodore Ts'o" <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Philippe Ombredanne <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: "Jason A. Donenfeld" <[email protected]>
Cc: Kate Stewart <[email protected]>
---
arch/x86/include/asm/stackprotector.h | 3 ++-
drivers/char/random.c | 5 ++++-
include/linux/random.h | 1 +
3 files changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/stackprotector.h
b/arch/x86/include/asm/stackprotector.h
index 371b3a4af000..4e2223aa34fc 100644
--- a/arch/x86/include/asm/stackprotector.h
+++ b/arch/x86/include/asm/stackprotector.h
@@ -72,7 +72,8 @@ static __always_inline void boot_init_stack_canary(void)
* there it already has some randomness on most systems. Later
* on during the bootup the random pool has true entropy too.
*/
- get_random_bytes(&canary, sizeof(canary));
+ if (crng_ready())
+ get_random_bytes(&canary, sizeof(canary));
tsc = rdtsc();
canary += tsc + (tsc << 32UL);
canary &= CANARY_MASK;
diff --git a/drivers/char/random.c b/drivers/char/random.c
index cd888d4ee605..003091d104bf 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -428,7 +428,10 @@ struct crng_state primary_crng = {
* its value (from 0->1->2).
*/
static int crng_init = 0;
-#define crng_ready() (likely(crng_init > 1))
+int crng_ready(void)
+{
+ return likely(crng_init > 1);
+}
static int crng_init_cnt = 0;
static unsigned long crng_global_init_time = 0;
#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
diff --git a/include/linux/random.h b/include/linux/random.h
index 2ddf13b4281e..45616513abd9 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -196,4 +196,5 @@ static inline u32 next_pseudo_random32(u32 seed)
return seed * 1664525 + 1013904223;
}
+extern int crng_ready(void);
#endif /* _LINUX_RANDOM_H */
--
2.14.3
